Cooperation in a fluid swarm of fuel-free micro-swimmers

While motile bacteria display rich dynamics in dense colonies, the phoretic nature of artificial micro-swimmers restricts their activity when crowded. Here we introduce a new class of synthetic micro-swimmers that are driven solely by light. By coupling a light absorbing particle to a fluid droplet we produce a colloidal chimera that transforms optical power into propulsive thermo-capillary action. The swimmers’ internal drive allows them to operate for a long duration (days) and remain active when crowded, forming a high density fluid phase. We find that above a critical concentration, swimmers form a long lived crowded state that displays internal dynamics. When passive particles are introduced, the dense swimmer phase can re-arrange to spontaneously corral the passive particles. We derive a geometrical, depletion-like condition for corralling by identifying the role the passive particles play in controlling the effective concentration of the micro-swimmers.

Multiple droplets on a conical fiber: formation, motion, and droplet mergers

Small droplets on slender conical fibers spontaneously move along the fiber due to capillary action. The droplet motion depends on the geometry of the cone, the surface wettability, the surface...

The influence of ground slab permeability on wall moisture in a historic buildingThe influence of ground slab permeability on wall moisture in a historic buildingThe influence of ground slab permeability on wall moisture in a historic buildingThe influence of ground slab permeability on wall moisture in a historic building

When impermeable ground bearing slabs are installed in old buildings without a damp-proof course, it is a common belief of practitioners within the conservation industry that ground moisture will be ‘driven’ up adjacent walls by capillary action. However, there is limited evidence to test this hypothesis. The accumulation of moisture in walls can promote the decay of the wall materials, decrease the thermal performance of the building envelope and adversely affect the comfort and health of occupants. An experiment was used to determine if the installation of a vapour-proof barrier above a stone flag floor in a historic building would increase moisture content levels in an adjacent stone rubble wall. This was achieved by undertaking measurements of wall, soil and atmospheric moisture content over a three-year period. Measurements taken using timber dowels showed that the moisture content within the wall did not vary in response to wall evaporation rates and did not increase following the installation of a vapour-proof barrier above the floor. This indicates that the moisture levels in the rubble wall were not driven by capillary rise.

Preparation of a Highly Porous Clay-Based Absorbent for Hazard Spillage Mitigation via Two-Step Expansion of Vermiculite

Expanded vermiculite (eVMT) has been studied as a risk-free, general-purpose absorbent for liquid hazards due to its excellent thermal and chemical stability. Here, vermiculite was expanded by two steps: exfoliation by 30 wt% H2O2 treatment at 60 °C and subsequent expansion by microwave heating. This two-step expansion produced more homogenously separated concertina-like eVMTs with a higher total pore volume of 7.75 cm3 g−1 than the conventional thermal method. The two-step eVMT was found to be greatly superior to the thermal and commercial silver counterparts in hazardous liquid-uptake performance. The uptake was simply interpreted as a physical infilling process of a liquid into the eVMT pores, and the spontaneous hazard removal with a great capacity was discussed with the large pore volume of two-step eVMT and its suitable pore dimensions for capillary action. As a practical device, a prototype absorbent assembly made of these eVMTs demonstrated the successful mitigation of liquid hazards on an impermeable surface.

A non-radioactive mass spectrometry based differential radial capillary action of ligand assay (DRaCALA) to assess ligand binding to proteins

Binding of ligands to macromolecules changes their physicochemical characteristics. Cyclic di-GMP and other cyclic di-nucleotides are second messengers involved in motility/sessility and acute/chronic infection life style transition. Although the GGDEF domain encoding preferentially a diguanylate cyclase represents one of the most abundant bacterial domain superfamilies, the number of cyclic di-GMP receptors falls short. To facilitate screening for cyclic di-nucleotide binding proteins, we describe a non-radioactive, MALDI-TOF based modification of the widely applied differential radial capillary action of ligand assay (DRaCALA). The results of this assay suggest that YciRFec101, but not the YciRTOB1 variant of the diguanylate cyclase/phosphodiesterase YciR binds cyclic di-GMP.

A Study of Bio-Computational Design in Terms of Enhancing Water Absorption by Method of Bionics Within the Architectural Fields

This essay aims to explore an architecture computational design intended to accept and absorb moisture through geometrical and material conditions, and using design strategies, help deliver this moisture upwards through capillary action to areas of cryptogamic growth including mosses and smaller ferns on the surface of architecture. The purpose of this research project is to explore the morphology of general capillary systems based on research into the principle of xylematic structures in trees, thereby creating a range of capillary designs using three types of material: plaster, 3D print plastic, and concrete. In addition, computational studies are used to examine various types of computational designs of organic structures, such as columns, driven by physical and environmental conditions such as sunshine, shade, tides and other biological processes to explore three-dimensional particle-based branching systems that define both structural and water delivery paths.